Add tests for providers.ExternalDependency & refactoring

objects/providers.py

@@ -184,31 +184,26 @@ class ExternalDependency(Provider):
 
     def __init__(self, instance_of):
         """Initializer."""
-        if not isinstance(instance_of, Iterable):
-            instance_of = (instance_of,)
         self.instance_of = instance_of
         self.dependency = None
         super(ExternalDependency, self).__init__()
 
     def satisfy(self, provider):
         """Satisfy an external dependency."""
-        self.dependency = provider
+        self.dependency = ensure_is_provider(provider)
 
     def __call__(self, *args, **kwargs):
         """Return provided instance."""
         if not self.dependency:
             raise Error('Dependency is not satisfied')
 
-        result = self.dependency.__call__(*args, **kwargs)
+        instance = self.dependency.__call__(*args, **kwargs)
 
-        is_instance = any((isinstance(result, possible_type)
+        if not isinstance(instance, self.instance_of):
-                           for possible_type in self.instance_of))
+            raise Error('{} is not an '.format(instance) +
-
-        if not is_instance:
-            raise Error('{} is not an '.format(result) +
                         'instance of {}'.format(self.instance_of))
 
-        return result
+        return instance
 
 
 class _StaticProvider(Provider):

tests/test_providers.py

@@ -376,6 +376,23 @@ class ExternalDependencyTests(unittest.TestCase):
 
     """ExternalDependency test cases."""
 
+    def test_call_satisfied(self):
+        """Test call of satisfied external dependency."""
+        provider = ExternalDependency(instance_of=object)
+        provider.satisfy(NewInstance(object))
+        self.assertIsInstance(provider(), object)
+
+    def test_call_satisfied_but_not_instance_of(self):
+        """Test call of satisfied external dependency, but not instance of."""
+        provider = ExternalDependency(instance_of=list)
+        provider.satisfy(NewInstance(dict))
+        self.assertRaises(Error, provider)
+
+    def test_call_not_satisfied(self):
+        """Test call of not satisfied external dependency."""
+        provider = ExternalDependency(instance_of=object)
+        self.assertRaises(Error, provider)
+
 
 class StaticProvidersTests(unittest.TestCase):